Such a locking system is known in particular from document FR-A-2 760 778. In that locking system, the control member is directly mounted to pivot on the plate about a second pivot pin distinct from the pivot pin of the latch. The control element thus begins by pivoting about the second pivot pin away from its locking position towards its unlocking position in such a manner as subsequently to allow the latch to pivot about its pivot pin away from its locked position towards its unlocked position. The presence of two pivot pins, and thus the presence of relative pivoting between the control member and the latch, requires manufacturing and assembly tolerances for the latch and the control member on the plate which are relatively constricting if it is desired to avoid the locking system becoming jammed in an intermediate position due to the latch accidentally being put into abutment with the control member in an intermediate position during their pivoting.